1. Field of the Invention
The present invention relates to level detection systems, in particular to fuel level detection systems.
2. Description of Related Art
Traditional liquid level measurement systems may use liquid level sensors to determine the point level of a liquid in the storage vessel. In some liquid measurement applications, such as fuel level in aircraft, for instance, precise knowledge of fuel level is needed to support, for example, automatic shutoff during refueling, independent low level warnings, and/or transfers between fuel storage tanks. One way of taking point level measurements is by using thermistor beads. Typically, these are negative temperature coefficient, wire wound resistors that are excited with a steady state current. Heat dissipation of the thermistor bead changes according to the wet/dry state of the bead, which in turn changes its resistance. This is sensed as a voltage change across the thermistor bead. Additionally, the response of two different thermistor beads operated at two different current levels can differentiate between the cold-dry and hot-wet conditions using lower current than that typically required to discriminate between these two conditions using a single thermistor.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for systems and methods that allow for improved liquid level sensing, for example, systems in flammable environments. The present invention provides a solution for these problems.